Which of the followig compounds has the lowest melting point?

Size of halide ion: ${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$

% of ionic Character: ${\mathrm{CaF}}_2>{\mathrm{CaCl}}_2>{\mathrm{CaBr}}_2>{\mathrm{CaI}}_2$

As the size of halide ion increases polarisability of anion increases distortion of electron cloud in anion increases and hence sharing property of electron cloud in Ca-X bond increases
$\therefore$ Covalent character increases, and hence ionic character decreases
→CaI₂ has least ionic character , hence it has least melting point 
Melting point of ionic compounds are greater than that of covalent compounds